Lhermitte-Duclos disease.

BACKGROUND: Lhermitte-Duclos disease (LDD; dysplastic gangliocytoma of the cerebellum) is a rare hamartoma of the cerebellum. It was first described by Lhermitte and Duclos in 1920 as "Sur un ganglioneurome diffus du cortex du cervelet" (Lhermitte and Duclos [Bull Assoc Fr Etude Cancer 9:99-107, 1920]). Since then, due to its rarity and the variability of its presentation, the diagnosis is often missed. It is not only important for the neurosurgeon and the pathologist to be aware of this entity so as to differentiate from malignant lesions but also to distinguish it from other cerebellar malformations, which may be hypoplastic or dysplastic, focal or diffuse in nature, with brain stem and cerebral involvement, and varied natural course. ILLUSTRATIVE CASE: We report a case of LDD in a 16-year-old boy. This case exemplifies the rarity of the disease leading to lack of awareness with which the diagnosis was easily missed. We also take this opportunity to discuss the clinical presentation, neuroradiological appearance, and a brief summary of histopathological findings, pathogenetic considerations, and neurogenetical aspects.